Hot gas defrostable refrigeration system



May 8, 1962 E. w. ZEARFOSS, JR 3,033,005

HOT GAS DEFROSTABLE REFRIGERATION SYSTEM 4 Filed Feb. 8. 1960 W W/ 5 T74? INVENTOR.

EZ/VE/F M ZEARFOLS JR.

HGENT United States Patent 3,033,005 HOT GAS DEFROSTABLE REFRIGERATION SYSTEM Elmer W. Zearfoss, Jr., Philadelphia, Pa., assignor, by

mesne assignments, to Philco Corporation, Philadelphia, Pa., a corporation of Delaware 1 Filed Feb. 8, 1960, Ser. No. 7,230

7 Claims. (Cl. 62-151) This invention relates to refrigeration and, more particularly, is concerned with apparatus of the type having provision for heating the evaporator to defrost the same.

It has been known to effect evaporator defrosting by by-passing the refrigerant flow restrictor of a refrigerating system and delivering directly to the evaporator hot gaseous refrigerant flowing from the compressor. Such arrangements are intended to result in condensation of the gaseous refrigerant within the evaporator, with resulting heating and consequent defrosting 0f the latter. Difliculties arise, however, in practice due for example to excessive accumulations of frost upon the evaporator surfaces that exceed the removal capabilities of the hot gas defrosting system. Also special means such for example as timers or counters, must be provided for controlling the by-pass line, and these elements complicate a system of this type.

With the foregoing in mind it is a broad objective of the invention to provide an improved apparatus for effecting hot gas defrosting of evaporator means.

It is a specific objective of the invention to provide a hot gas defrosting system which not only is highly effective in producing adequate defrosting, but which system also is extremely simple and inexpensive.

It is still another objective of the invention to provide simple and effective means for defrosting the evaporator upon the initiation of each operating cycle of the motor compressor, at which time the evaporator advantageously is at its highest temperature and has the least accumulation of frost thereon.

In the achievement of the foregoing objectives, the invention contemplates, in novel combination with a bypass conduit or connection serving to deliver hot gaseous refrigerant to the evaporator means, provision of a selfactuating valve disposed within such by-pass connection leading to the evaporator means, and operable upon operation of the compressor, to accommodate flow of refrigerant between the compressor and the evaporator means to defrost the latter. In particular accordance with the invention, the means controlling the by-pass line includes a novel valve that is closed in response to a predetermined refrigerant flow rate (pounds per unit of time) through the same. This refrigerant flow rate corresponds to that pressure Within the evaporator which ob tains under temperature conditions under which com-- plete defrosting will take place. As this predetermined flow rate is attained the valve automatically closes the bypass line whereupon the normal refrigeration cycle may begin. Preferably, each cooling cycle is accompanied by defrost of the evaporator.

The objects and features of the invention, together with significant details of construction thereof, will be more fully understood from a consideration of the following description, taken in conjunction with the accompanying drawing, in which:

FIGURE 1 is a diagrammatic representation of a refrigeration system disposed within a cabinet, and including defrosting apparatus embodying the present invention;

FIGURE 2 is a somewhat enlarged sectional showing,

with parts broken away, of apparatus seen in FIGURE 1; FIGURE 3 is a showing similar to FIGURE 2 and illustrating an operational feature of the invention;

FIGURE 4 is a showing similar to that of FIGURE 2 3,033,005 Patented May 8, 1962 and illustrating a modified embodiment of the invention; and

FIGURE 5 is a showing similar to FIGURE 3 and illustrating an operational feature of the modified embodiment. I

Now making detailed reference to the drawing, it will be seen that the illustrated embodiment of the invention includes the elements of a refrigerating system of conventional single evaporator type, said system having a motor compressor 10, a condenser 11, a continuously open restricted connection or capillary tube 12 and an evaporator 14 disposed in heat exchange relation with a upper and lower temperatures, respectively, of, evaporator A by-pass connection of conduit 16 extends between the inlet of condenser 11 and the inlet of evaporator 14. By-pass conduit 16 is controlled, in accordance with the invention, by valve means 17 disposed in series flow circuit therewith and actuatable, in a novel simple, and automatic manner hereinafter to be described, to open and close conduit 16.

Making reference further to FIGURES 2 and 3, valve means 17 comprises a housing 21 having a vertically extending bore 22. An inlet port 23 extends through housing 21 and communicates with bore 22 in a lateral region thereof. The portion of by-passconduit 16 connected with the inlet to condenser 11 leads into port 23. An

outlet port 24 leads from bore 22, at a point above inlet comprising a float 27 and a weighted portion 31 affixed thereto by a stem 32 disposed in a region opposite inletv port 23. Plunger 26 is disposed and-adapted for vertical movements within bore 22, and float 27 includes a sealing portion 28 and a cylindrical surface portion 33, the latter having a diameter slightly less than bore 22 thereby providing a restrictive uniform annular area A permitting flow of gaseous refrigerant from inlet port 23, through bore 22, thence to outlet port 24. Sealing portion 28 is movable into and out of sealing engagement with valve seat 25.

In operation of the apparatus, as the compressor starts to run in response to closing of thermostatically operated switch 19, gaseous refrigerant by-passes condenser 11 and capillary tube 12, due to the restrictive nature of the latter, and is fed through valve means 17 via its inlet port 23, bore 22 and outlet port 24, plunger 26 being then in its initial or rest position shown in FIGURE 2. Relatively hot gaseous refrigerant, following the path of least resistance, is discharged directly from compressor 10 into evaporator 14 to give up heat thereto and defrost the same. This hot gas flows upwardly through the area A,

such area permitting sufficient flow of gaseous refrigeranttemperature (32 F.) of the frost being removed. Cooled refrigerant then flows through the suction line 15 into the housing of motor-compressor 10, where it is reheated and compressed and again caused to flow through by-pass conduit 16 After the frost has melted, the temperature of the still relatively cold evaporater again starts to increase. Accordingly, the density of the gaseous refrigerant flowing through valve means 17 attains a predetermined higher value, reflecting the temperatures existing upon completion of defrost. This density value is great enough to retard flow of refrigerant through area A to a degree sufficient to raise the pressure of refrigerant entering port 23 and lift valve plunger 26, overcoming weight 31. Sealing portion 28 is therefore raised to become seated against valve seat 25 to close by-pass conduit 16. In tests conducted on apparatus made in accordance with the disclosure, at 32 p.s.i.g. evaporator pressure, the increased flow rate of refrigerant, by virtue of increased density thereof, through valve means 17 created suffic-ient force on plunger 26 to move it upward to seat the same, this pressure corresponding to evaporator temperatures appreciably above 32 F. at which the frost melted and was completely removed.

Closure of the by-pass conduit then restores normal circulation of refrigerant through condenser 11 and capillary tube 12. Valve means 17, will remain closed, that is in its upper position, throughout the remainder of the normal refrigerating cycle due to the relatively high pressure differential created by restrictive capillary tube 12 between inlet port 23 and outlet port 25. Upon cooling the evaporator to a predetermined desired value, switch 19' is thermostatically opened to deenergize compressor 10. The pressures within the closed system, and exerted on valve plunger 26 via ports 23 and 24, then equalize and permit the plunger to be drawn downwardly by weight 31 out of sealing position. The system is then ready for the next defrosting operation when switch 19 is closed to initiate operation of the compressor.

Referring to the embodiment ofthe invention shown in FIGURES 4 and 5, valve plunger 26a has a weighted portion 31a formed of a magnetic material. Closely encircling aud frictionally supported, by suitable means (not shown), upon the narrowed-down lower portion 35 of non-magnetic valve-housing 21a is a permanent magnet 34 adapted to be selectively positioned relative to magnetic weighted portion 31a, thereby to provide for calibrating the pressure responsive valve means in accordance with defrost cycle performance requirements. Calibration is of course accomplished by varying the hold-down force of the magnet upon plunger 26a, by varying the position of the magnet with respect to the plunger.

FIGURES 4 and also show additional modifications wherein the sealing portion 28a of float is made of resilient material to conform with the upper portion of housing 21a to insure perfect sealing of outlet port 24a when the float is in its uppermost position (FIGURE 5).

While the invention has been diagrammatically illustrated as being embodied in one form of refrigerator apparatus, it Will be understood that it has utility in a variety of refrigerating apparatus requiring periodic defrosting of the evaporator. Furthermore, while the means 16 is shown and described as by-passing the entire condenser 11, it will be understood that the by-pass connection 16a might, in certain embodiments, be connected at some other point in the system. The important consideration is that the restrictor 12 be by-passed and that the inlet 16a of the by-pass conduit be so located as to receive gaseous refrigerant when flow through the conduit 16 occurs. The invention contemplates the foregoing, and such other modifications ascome within the scope of the appended claims.

I claim:

1. A refrigeration system comprising: a compressor, a condenser, a restrictor, and evaporator connected in series flow circuit; means by-passing said restrictor and adapted to deliver to said evaporator hot gaseous refrigerant flowing from said compressor; and refrigerant flow control means including a valve constructed and located to control flow through said by-pass means and operative, when the compressor is operating, to provide modified flow of hot gaseous refrigerant through said by-pass means into said evaporator for a time period sufficient to defrost the latter, said valve being further operative automatically after such period, and in response to an increase in density of the refrigerant corresponding to temperature conditions prevailing in the evaporator when it has become defrosted, to close said by-pass means and to establish normal flow of refrigerant through said condenser and said restrictor thereby to effect cooling of said evaporator, said valve including a compartment provided with inlet and outlet ports communicating with said compartment and said by-pass means, and plunger means disposed within said compartment and adapted for movement between a pair of positions to open and to close said outlet port, and consequently said by-pass means, said valve plunger means being movable by the refrigerant after such period of modified flow to close said port and bypass means in response to the recited increase in refrigerant density in system, thereby to establish such normal flow of refrigerant.

2. A refrigeration system comprising: a compressor, a condenser, a restrictor, and evaporator connected in series flow circuit; means by-passing said restrictor and adapted to deliver to said evaporator hot gaseous refrigerant flowing from said compressor; and refrigerant flow control means including a valve constructed and located to control flow through said by-pass means and operative, when the compressor is operating, to provide modified flow of hot gaseous refrigerant through said bypass means into said evaporator for a time period sufficient to defrost the latter, said valve being further operative automatically after such period, and in response to an increase in density of the refrigerant corresponding to temperature conditions prevailing in the evaporator when it has become defrosted, to close said by-pass means and to establish normal flow of refrigerant through said condenser and said restrictor thereby to effect cooling of said evaporator, said valve including a vertically extending bore provided with an inlet port disposed in fluid flow communication with the outlet of said compressor and an outlet port disposed above the lover of said inlet port and in fluid flow communication with the inlet of said evaporator, valve seat means associated with said valve outlet port, and a valve plunger disposed within said bore between said ports and adapted for movements into and out of engagement with said valve seat means, respectively to close and to open said outlet port, said valveplunger being so constructed and cooperatively disposed with respect to said bore as to be movable by refrigerant to close said port, in response to the mentioned increase in refrigerant density, to establish such normal flow of refrigerant.

3. A valve in accordance with claim 1, wherein said plunger means includes a portion that is ferromagnetic, and a magnet is disposed and adapted to exert a restraining force on said plunger means, said magnet being movably mounted selectively to modify such restraining force, whereby force required of the refrigerant to move said plunger meansmay be modified.

4. A valve in accordance with claim 1 wherein said plunger means is of ferromagnetic material, and a magnet is adjustably positioned adjacent the said plunger means and adapted forcibly to attract the same, adjustment-of the magnet being effective to modify the attractive force thereof on the plunger means in opposition to and in accordance with refrigerant pressure tending to move the plunger means to closed position.

5. A refrigeration system comprising: a compressor, a, condenser, a restrictor, and evaporator connected in series flow circuit; means for 'by-passing said" restrictor and adapted to deliver to said evaporator hot gaseous refri erant flowing from said compressor; a valve body including a compartment ovided with inlet and outlet ports communicating with said compartment and with said lay-passing means; and plunger means disposed within said valve compartment and adapted for move ments between a pair of positions to open and to close said outlet port and consequently said by-passing means, thereby to control flow of refrigerant through said bypassing means and operative to provide a substantial flow of hot gaseous refrigerant through said lay-passing means into said evaporator to defrost the latter when the compressor is operating, said valve plunger means being movable by said refrigerant to close said port in response to a predetermined increase in refrigerant density in said system corresponding to temperatures prevailing in said system when said evaporator has become defrosted thereby to establish flow of refrigerant through said condenser and said restrictor and effect cooling of said evaporator.

6. In a refri eration system of the type having elements including a compressor, a condenser, a restrictor, and an evaporator, connected in series flow circuit, means for by-passing said restrictor and adapted to deliver to said evaporator hot gaseous refrigerant flowing from said compressor, comprising: a passage communicating with the discharge side of said compressor and with said evaporator; and valve means constructed and located to control flow through said passage and including port means communicating with said passage, and plunger means operative to open said port means, upon initiation of compressor operation, to establish a substantial period of modified flow of hot gaseous refrigerant through said passage into said evaporator to elevate the temperature of and to defrost the later, said plunger means being further operative by said refrigerant to close said port means, in response to an increase in the density of the refrigerant flowing through said valve means at an elevated temperature, to interrupt flow through the recited passage and to reestablish normal flow of refrigerant through the condenser, the restrictor, and thence to the evaporator.

7. In a refrigeration system of the type having elements including a compressor, a condenser, a restrictor, and an evaporator, connected in series flow circuit, means for lay-passing said restrictor and adapted to deliver to said evaporator hot gaseous refrigerant flowing from said compressor, comprising: means defining a pas sage communicating with the discharge side of said com pressor and with said evaporator; and valve means con structed and located to control flow through said passage and including port means communicating with said passage and movable means operative to open said port means, upon initiation of compressor operation, to establish a substantial period of modified flow of hot gaseous refrigerant through said passage into said evaporator to elevate the temperature of and to defrost the latter, said movable means being further operative by said refrigerant to close said port means, in response to an increase in the density of the refrigerant flowing through said valve means at an elevated temperature, to interrupt flow through the recited passage and to establish flow of refrigerant through the condenser, the restrictor and thence to the evaporator.

References Cited in the file of this patent UNITED STATES PATENTS 2,049,625 Ruppricht Aug. 4, 1936 2,579,439 Noe Dec. 4, 1951 2,694,904 Lange Nov. 23, 1954 2,907,181 Nonomaque Oct. 6, 1959 

